In remotely controlling servo-motor mechanisms, there is a distinct need for control devices that are responsive to an electrical current varied according to a pattern determined at a control station and used to control remotely located mechanisms. For example, in the operation of a brake system of one vehicle connected with another having an operator's station, present technology provides satisfactory pressure-sensing transducers and transducer signal amplification equipment which can be located in the controlling vehicle but unsatisfactory equipment components responsive thereto for directly controlling a hydraulic braking system on the remotely controlled vehicle. This is merely one of many instances in which highly accurate, highly-responsive control action is needed in the translation of electrical signals of varying strengths into the operation of remotely controlled servo-mechanisms.
It is a primary object of the invention to provide a control device in the form of a specially constructed solenoid valve for regulating the pressure in a statically pressured body in a manner proportional to the energy input of the solenoid. Another object anallary to the above object is to obtain output pressures of the valve which may vary over any range between a supply pressure greater and a supply pressure lesser than the pressures of such range. Another object anallary of the foregoing object is to obtain modulated output pressures which are accurately correlated with the strength of the current for energizing the solenoid through the use of frictionless mechanism. It is also an object to provide a valve design enabling the manufacturing of parts of the valve within generous dimensional tolerance levels to achieve low manufacturing expense. A further object is to utilize spring mechanism within the valve which is insensitive to temperature changes and permits the use of springs manufactured to spring rates within generous tolerances. Still another object is to match a spring mechanism with the solenoid mechanism in such a way as to balance off a solenoid plunger rate with the spring rate of the spring mechanism and thus enable the modulation rate of the valve to be proportional in a high degree to the strength of the electrical current imposed on the coil of the solenoid.